Field
The present disclosure relates to the field of tire manufacture. More specifically, the disclosure relates to the manufacture of tires the tread of which comprises a plurality of raised elements comprising on at least one of their lateral faces a cover layer.
Description of Related Art
It is known practice to design tires the tread of which comprises various rubber compounds. Document WO 03089257 discloses such treads. More specifically document WO 03089257 discloses a tread comprising raised elements. Each raised element comprises a contact face intended to come into contact with a ground when the tire is rolling along, and lateral faces connected to the contact face. All or part of the lateral faces of these raised elements are coated with a cover layer. The material of which this cover layer is made differs from the rubber compound of which the tread is made. This material notably has wet grip that is far superior to the wet grip of the rubber compound. This allows a very appreciable improvement in cornering on wet surfaces.
One method of manufacturing this tread is notably disclosed in document WO 2006069912. According to this method of manufacture, in a first step, provision is made for the material intended to constitute a cover layer to be injected in the form of one or more inserts into the green tire using an injection nozzle. The insert or inserts is or are then shaped, in a second step, by ribs of a vulcanizing mold, so that they cover lateral faces molded by the ribs.
This method of manufacture does have its limits. Specifically, while it is being shaped, the insert experiences significant shear force from the rib with a view to converting this insert into a layer of lesser thickness. This shear force may cause cracking within the insert and this makes control of the movements of the material of which this insert is made more difficult. The shape and thickness of the cover layer thus formed may therefore be somewhat haphazard. The advantages afforded by the layer to the performance of the tire are therefore reduced.
In addition, in this method of manufacture, it is necessary to align the inserts with the ribs. This then makes the manufacture of the tread more complicated.
There is therefore a need to improve the laying of a cover layer on a lateral face of a raised element belonging to a tire tread.